If you set up your DNS to use wildcards, then assigning * to 68.222.222.22 would make it so that any of the subdomains would work provided there is a virtual host or something similar set up to route the subdomains somewhere.

If set up properly, docs.domain.com, mail.domain.com, www.domain.com, subdomain.domain.com, etc, would all work.

You would use your web server (Apache, IIS, etc..) to designate where the subdomains went.